# Verification of this phase change modeling

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 December 15, 2011, 01:20 Verification of this phase change modeling #1 New Member   kawamura Join Date: May 2011 Location: Ishikawa,Japan Posts: 7 Rep Power: 15 Hi everyone. I'm trying to two phase flow with phase change using VOF method. There are some approach for mass transfer modeling. I'm interested in the following way. mDot = K/L * grad(T)・grad(F) Note that K refers to the mixture thermal conductivity, F refers to the volume fraction and L is the latent heat. But I couldn't find that verification. If you understand this correctry, please let me know the verification! Thanks a lot.

 December 20, 2011, 01:54 #2 Member   Masashi Ohbuchi Join Date: Oct 2009 Posts: 74 Rep Power: 16 Hi, Kawamura-san, I can not make a verification for this notation. But I think grad(F) should be grad(F)/mag(grad(F)). This means unit normal vector of interface.

 December 20, 2011, 03:46 #3 New Member   kawamura Join Date: May 2011 Location: Ishikawa,Japan Posts: 7 Rep Power: 15 Hi Ohbuchi-san, thanks for your response. but FLUENT and some people show this expression in their paper . there is non-existence of normal vector. I think the most accurate expression is... mDot = 1/L *(qg-ql)・n *Aint/V (kg/m^3 /s) in evaporating where qg and ql is heat flux in gas and liquid phase respectively,Aint is interface area,V is volume of cell and n is unit normal vector. but getting the correct interface area is so difficult in VOF. so I think that grad(F) may works as n・Aint/V . but i don't get a correct understanding about this

 December 20, 2011, 23:59 #4 Member   Masashi Ohbuchi Join Date: Oct 2009 Posts: 74 Rep Power: 16 Hi. Kawamura-san, The value of grad(F) will be very large on sharp interface, so I think some limiter function will be needed to restrict the value within 0-1. And, I think it's impossible to determine interface area from grad(F) without assuming specific flow regime(such as stratified flow or bubbly flow). BTW, the expression of mas transfer by heat transfer; mDot = (k/L) grad(T) grad(F)/mag(grad(F)), was originally introduced in following paper. Son,G. and Dhir,V.K. A level set method for analysis of film boiling on an immersed solid surface. Nummer. Heat Transfer B,vol.52,pp.153-177.(2007) This expression is only valid on stratified flow regime.

 December 21, 2011, 00:14 #5 New Member   kawamura Join Date: May 2011 Location: Ishikawa,Japan Posts: 7 Rep Power: 15 Hi Ohbuchi-san, It's useful information for me! Now it's starting to make sense. I consider about assuming specific flow. Thank you for your kindness. Kawamura

 Tags phase change, vof